Specimen heating and positioning device for an electron microscope

ABSTRACT

A specimen heating and positioning device having a specimen stage with a specimen holder mounted thereon. The specimen stage positions the specimen at the optical axis. The specimen holder, including a specimen and heating coil, is disposed so that the shifting of the specimen holder due to thermal expansion or contraction is offset by a corresponding shifting of the specimen stage.

United States Patent Nukui et al.

[ SPECIMEN HEATING AND POSITIONING DEVICE FOR AN ELECTRON MICROSCOPE[75] Inventors: Shigeru Nukui, Saitama; Hideaki Mikazuki, Tokyo, both ofJapan [73) Assignee: Nihon Denslii Kabushiki Kaisha,

Tokyo, Japan [22] Filed: Dec. 5, 1973 21 Appl. No.1421,978

{30] Foreign Application Priority Data Dec. l4, I972 Japan 47-143726[52] U.S. Cl 250/442; 250/443 [51] Int. Cl. H0lj 37/20 [58] Field ofSearch 250/439, 440, 44l, 442,

[56] References Cited UNITED STATES PATENTS 2,753,458 7/l956 Kazato etal. 250/443 [451 July 22, 1975 12/1973 Mikajiri 250/442 PrimaryExaminer-James W. Lawrence Assistant Examiner-C. E. Church Attorney,Agent, or Firm-Webb, Burden, Robinson & Webb [5 7] ABSTRACT 4 Claims, 5Drawing Figures SPECIMEN HEATING AND POSITIONING DEVICE FOR AN ELECTRONMICROSCOPE The present invention relates to a specimen heating andpositioning device for electron microscopes or the like.

A specimen must be set in a magnetic field of an objective lens for highresolution electron microscopy. In such case, a device for positioningthe specimen can be classified into two types with respect to the way ofinsertion of the specimen. One is the top entry type in which thespecimen is inserted from an upper part of an objective lens, andanother is the side entry type in which the specimen is insertedlaterally into the objective lens. Both types have respective features,but the side entry type is now used more frequently because of easyoperation providing larger angles of tilt than the top entry type. Fromanother viewpoint, since one end of a side entry specimen stage is heldto a microscope column, the distance between the column and the specimenmust be extremely long.

For this reason, the specimen largely drifts perpendicularly away fromthe optical axis as the thermal expansion or contraction due to thechange in temperature at the specimen stage occurs; it follows,therefore, that in observation of the specimen being heated, itsresolving power remarkably lowers due to the drift.

An advantage of this invention is therefore to provide a specimenheating device for electron microscopes capable of observing the heatedspecimen with high resolving power.

Another object of this invention is to provide a specimen heating devicefor electron microscopes or the like, which is capable of compensatingthe drift of a specimen due to the thermal expansion or contraction ofthe specimen stage.

Briefly, according to this invention, a specimen heating and positioningdevice for an electron microscope or the like comprises a specimen stageadjustably fixed to the microscope column for positioning the specimenalong the optical axis. The stage is arranged to expand on heating alongan axis perpendicular to the optical axis and away from a firstreference point fixed relative to the optical axis. A specimen holder ismounted in the specimen stage. The holder is arranged to expand onheating along the same axis along which the specimen holder expands awayfrom a second reference point fixed relative to the specimen stage andon the opposite side of the optical axis from the first reference point.Means are provided for heating the specimen. The distances between thereference points and the optical axis can be selected such that as thespecimen holder and specimen stage are heated, the thermal expansion ofthe specimen stage and the specimen holder are approximately equal, thusmaintaining the specimen substantially at the optical axis.

Other objects and advantages of the present invention will be betterunderstood from the following detailed description referring to theaccompanying drawings in which:

FIG. 1 is a cross-sectional view of one embodiment of this invention;

FIG. 2 is a plane view showing a substantial part in FIG. 1;

FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2;

FIG. 4 is a cross-sectional view taken along line B-B in FIG. 2; and,

FIG. 5 is a cross-sectional view showing another embodiment of thisinvention.

Referring to FIG. I, a section of a microscope column l, for example,the objective lens yoke has mounted therein a rotating body 2 rotatableabout an axis intersecting the electron optical axis of the microscopeperpendicular thereto (hereafter the X axis" as shown on the drawing). Aknob 3 attached to the external end of the rotating body 2 serves torotate the body 2 about its X axis. A supporting member 5 terminating ona sphere 4 is supported in a spherical socket of the rotating body 2 sothat it is rotatable about a center in the sphere 4. A screw 6 threadedin the rotating body, and the tip of the screw directly touches a sideof the supporting member 5. The rotating body 2 is biased against thescrew by a spring 7.

A specimen stage 8 passes through the said supporting member 5 and ispositioned across the optical axis. A specimen holder 9 is mounted inthe specimen stage to be positioned at or near the optical axis. An endof the stage abuts a connecting rod 11 through a ball or bearing I0 madeof thermally insulating material as ruby. The connecting rod is setinside a cylinder 12 disposed in the column 1 and is capable of shiftingthrough the cylinder 12 in a longitudinal direction, and may also beslightly tilted within the cylinder 12. The end of this cylinder outsidethe column touches a bell crank 14, positionable by a screw 15. Thus, byturning the knob 3 of the rotating body 2, the supporting member S, andthe stage 8 turn about the axis X and the specimen is tilted in acertain direction and at a certain angle with respect to the axis X.Further, by adjusting the screw 6, the supporting member 5 rotatescentering the sphere 4. Accordingly, the specimen is moved along theaxis Y perpendicular to the X axis. Again, adjusting the screw 15, thestage 8 or the specimen shifts in a direction of the axis X through themovement of bell crank 14, the cylinder 12 and the connecting rod 11.

The present invention is characterized by a mechanism which holds thespecimen holder 9 to the specimen stage 8. In FIGS. 2, 3, and 4 anopening I6 bigger than the specimen holder 9 is formed in the specimenstage 8 and the said holder is accommodated in this hole, supported byballs 17a, 17b, 17c and 17d made of thermal insulating material such asruby. A pair of cone-shaped sockets 18a and 18b and a pair of V- shapedgrooves and 1% are cut into opposite sides of the specimen holder 8. Inthis case, the cone-shaped sockets 18a and 18b are, in FIG. 2, formed onthe right side of the optical axis Z, perpendicular to axes X and Y,namely, on the side opposite the side where the end of the stage 8touches the connecting rod 11 thus placing the optical axis between saidsockets 18a and 18b and said end. The balls or bearings 17a and 17b areaccommodated in the cone-shaped sockets 18a and 18b, respectively, whilethe balls 17c and 17d are positioned in the V-shaped grooves 19a and19b, respectively, and all bearings are kept in position by screws 20a,20b, 20c and 20d respectively, (20a and 20b not shown). As a result, thecontact points of the balls 17a and 17b are fixed on the stage 8; whilethe balls 17c and 17d can be freely shifted permitting the specimenholder to expand away from sockets 18a and 18b.

In the center of the specimen holder is a specimen cartridge 23 whichincludes the specimen 21 and a heating coil 22 held by grooves and rubyballs 24a, 24b and 24c placed therein.

In this embodient, provided an electric current is supplied to theheating coil 22 to heat the specimen 21 up to high temperature, forexample l,0() C, the specimen holder 9 and the specimen stage 8 areheated (in spite of being supported by the balls 17a, l7b, 17c, 17d,24a, 24b and 24c made of thermal insulating material) by slight thermalconduction and radiation. Thermal expansion, of course, results. Theheating device according to this invention is designed so that theexpanding directions of the stage 8 and the holder 9 are opposed and thespecimen has little, if any drift.

Since the stage 8 thermally expands away from the contact point of itstip with the connecting rod 11, the center of the specimen 21 shifts tothe direction shown by an arrow marked C in FlG. 2. The degree of thisshift for this case corresponds to the thermal expansion of the length lH where l, is a distance between the center of the specimen and thecontact point above described, 1 is the distance between the center ofthe specimen and the ruby balls 170 or 17b, measuring these distancesalong the shifting axis.

On the other hand, the specimen holder 9 expands to reverse direction ofthe arrow marked C, away from the ruby balls 17a and 17b, thus thecenter of the specimen shifts in the same direction in an amountcorresponding to the thermal expansion for the length 1 If the shiftingdistances due to the thermal expansion of both mem bers are equal byvirtue of pertinent selection of their dimensions and materials, thedrift of the specimen can be substantially prevented. Since thetemperature of the specimen holder will be much higher than that of thespecimen stage, even if these members are made of identical material,the center of the specimen can be held at a stationary position.

We have found that where the specimen stage 8 and the specimen holder 9were both made of phosphor bronze and the specimen was heated to l,000C, the temperature of the specimen stage and the specimen holder wereincreased 98 C and 495 C with respect to the temperatures beforeheating. No drift in the center of the specimen occurred provided theaforementioned length I was l9mm and 1 was 4.7 mm.

FIG. shows another embodiment of this invention. In this embodiment aheater 25 is also accommodated into the specimen stage. This heater isused in order to heat the stage 8 up to a certain temperature prior tothe observation of a heated specimen by electron microscope. By virtueof this preheating the stage, the period of time required for reachingthe thermal equilibrium stage during heating the specimen can beshortened, and hence also even a slight drift during equilibrium can beexcluded.

in this embodiment, the position of the heater 25 is not limited to theend of the stage 8 as shown in the drawing, but may be adjacent to thespecimen holder 9. In addition, it is preferable to arrange any thermalinsulator between the specimen stage 8 and the supporting member 5 toprevent heat conduction to the column 1.

In the practical application of this invention. diverse modificationsmay be realized. For instance, though a fixed point of the specimenstage 8 was previously selected at its tip, it may be on the right ofthe axis Y in FIG. 1. Further, the specimen holder and the specimencartridge which were independently formed as in the earlier embodiment,may be unitary or integral.

Having thus described the invention with the detail and theparticularity as required by the Patent Laws, what is desired protectedby Letters Patent is set forth in the following claims.

We claim:

1. A specimen heating and positioning device for an electron microscopeor the like having an electron optical axis comprising a specimen stageadjustably fixed for positioning a specimen along the optical axis, saidstage arranged to expand on heating on an axis passing through theoptical axis away from a first reference point fixed relative to theoptical axis and spaced therefrom, a specimen holder mounted in saidspecimen stage for holding the specimen and arranged to expand onheating along the same axis along which the specimen stage expands in adirection away from a second reference point fixed relative to thespecimen stage and on the opposite side of the optical axis from thefirst reference point, means for heating the specimen, the distancesbetween the reference points and the optical axis being selected suchthat as the specimen holder and specimen are heated, incidental to theheating of the specimen, the expansion of the stage and holder areapproximately equal thus maintaining the specimen substantially at theoptical axis.

2. A specimen heating device according to claim 1 in which means areprovided for heating the specimen stage.

3. A specimen heating and positioning device according to claim 1wherein the said specimen holder is held on the said specimen stage bybearings made of thermal insulating material.

4. A specimen heating device according to claim 1 wherein the specimenholder mounted in said specimen stage is secured by four ball bearings,two bearings being seated in cone-shaped sockets formed on oppositesides of the said specimen holder and the adjoining portions of thespecimen stage therein defining the second reference point and two beingpositioned in V- shaped grooves on opposite sides of the specimen holderand adjoining portions of the specimen stage.

IF I. i

1. A specimen heating and positioning device for an electron microscope or the like having an electron optical axis comprising a specimen stage adjustably fixed for positioning a specimen along the optical axis, said stage arranged to expand on heatinG on an axis passing through the optical axis away from a first reference point fixed relative to the optical axis and spaced therefrom, a specimen holder mounted in said specimen stage for holding the specimen and arranged to expand on heating along the same axis along which the specimen stage expands in a direction away from a second reference point fixed relative to the specimen stage and on the opposite side of the optical axis from the first reference point, means for heating the specimen, the distances between the reference points and the optical axis being selected such that as the specimen holder and specimen are heated, incidental to the heating of the specimen, the expansion of the stage and holder are approximately equal thus maintaining the specimen substantially at the optical axis.
 2. A specimen heating device according to claim 1 in which means are provided for heating the specimen stage.
 3. A specimen heating and positioning device according to claim 1 wherein the said specimen holder is held on the said specimen stage by bearings made of thermal insulating material.
 4. A specimen heating device according to claim 1 wherein the specimen holder mounted in said specimen stage is secured by four ball bearings, two bearings being seated in cone-shaped sockets formed on opposite sides of the said specimen holder and the adjoining portions of the specimen stage therein defining the second reference point and two being positioned in V-shaped grooves on opposite sides of the specimen holder and adjoining portions of the specimen stage. 